Interposer assemblies with molded plastic plates and inserted metal contacts in the plates are used for forming electrical connections between contact pads on opposed substrates. The contacts are spaced very close together in land grid array rows and columns to establish a large number of differential pair signal connections and ground connections extending through the plate.
Increased circuit speed requires transmission of differential signals through interposer plates at signal frequencies of 10 or more gigahertz. Transmission of high-frequency signals through conventional interposer plates with short, closely spaced contacts and very fast rise times for the signals increases signal impedance and degrades signal strength. Further, high-frequency signaling can cause cross-talk between adjacent pairs of signal contacts.